| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have been [prep] | 294 |
|
| 2 | must have been [prep] | 294 |
|
| 3 | [modal v] have been on | 129 |
|
| 4 | must have be on | 20 |
|
| 5 | must have [been] on | 20 |
|
| 6 | must have been on | 20 |
|
| 7 | must [verb] been on | 20 |
|
| 8 | must have [be] on | 20 |
|
